High-Accuracy Measurement of the Spin-Dependent Neutron Scattering Length of the Deuteron

The experiment aims at a significant improvement of accuracy of the doublet nd scattering length a₂, which at present is only poorly known. The expected result will provide a key input to theoretical descriptions of few-nucleon systems, both in potential models and new effective field theory approaches. The value of a₂ is obtained from a linear combination of the spin-dependent nd scattering length, a_i,d, and the spin-independent one, a_c,d. Whereas the latter is rather well known, the former is limiting the total accuracy. We plan to measure a_i,d with 10^-3 accuracy at PSI using the technique of nuclear pseudomagnetic precession of polarised neutrons in a polarised target. The set up and test of the Ramsey apparatus, which will be employed to detect the pseudomagnetic precession, is described here.